Fluorescent light dimming system



April 16, 1963 E. w. BANIOS 3,086,140 muoasscsm LIGHT 01mm; SYSTEM FiledMay 26, 1960 I4- 2 I6 52 3o w, 57 ,;0

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particularly when the lights are dimmed, as to obviate 3,086,140FLUORESCENT LIGHT DIMMING SYSTEM Edward W. Banios, Hawthorne, Calif.,assignor to Douglas Aircraft Company, Inc., Santa Monica, Calif. FiledMay 26, 1960, Ser. No. 31,960 1 Claim. (Cl. 315-98) This inventionrelates to fluorescent lamps and systems, particularly those inaircraft.

More especially, it deals with fluorescent lighting in aircraftpropelled by jet engines, in which A.C. generating systems are normallyavailable.

Still more particularly, this invention is concerned with jet-aircraftfluorescent lighting systems employing 13-watt T-S lamps, althoughunstable,

reflections from the pilotss windscreens, or to enable passengers tosleep, are, for many well known reasons, currently the preferred type offluorescent lamp. Among these reasons is the fact that the T-5 exhibitsthe highest ratio of light output and intensity to its weight of allratings of fluorescent lamps.

The conventional T-S or other such lamp will either go out, flicker,jitter, oscillate or exhibit striations of light and opacity upon beingdimmed, as for the present purposes.

This invention is predicated upon, among other considerations, thediscovery that rapid-start and consistent lamp re-ignition at eachsemi-cycle of the A.C. supply voltage are essential in order to obviatemost of the aforestated defects and to assist in alternate and rapidlyoccurring dimming followed by full lighting.

Broadly to achieve these particular functions (rapidstart and consistentlamp re-ignition), the lamp filaments are continuously energized, evenduring the dimming phase, thereby to make available at all times at thelamp filaments an abundance of electrons, to always enable establishmentof an arc thru the inert gas from filament to filament.

Further to these and other ends, means are provided for suddenly peakingthe voltage at the end of each halfcycle of the A.C. voltage (whetherthe lamp is dimmed or not), the peak being of unusually low total energybut of high-or sufficiently high-amplitude. The latter means, in oneembodiment, may take the form of one or more saturable, voltage peakingtransformers in the basal circuits. Generalized, the invention thusprovides a steep lamp voltage wave-front, having a sufiicient amplitudeto efiect infallible re-ignition of the lamp at the same phase angle ofeach A.C. semi-cycle. The peakingtransformer arrangement acts herein asa filament transformer and also cooperates with the lamp ballastingmeans.

Objectionable striations are minimized by means which overcome thedetrimental effects of impurities in the inert gas of the lamp and thefluorescible coating on the inside of the tube wall. These effectsoperationally combine with the effects of gas pressure, temperature andfragile or improper electrode configuration to cause this highlyobjectionable striating. One form of means contemplated to achieve thisend includes unusually heavy electrical ballasting of the lamp, asdetailed hereinafter. Preferably, an inductive impedance ballast isemployed. Also,

at low and medium lamp-current operation, a high series impedancearrangement is rendered effective hereby. One form of means contemplatesthe use of a secondary-ballast arrangement for the peaking transformer.

To obviate discontinuities throughout the dimming range, a proper lampvoltage wave shape is provided and smooth transition of voltagewaveshape in the lamp during change in current in the lamp is producedwith the peaking transformer arrangement.

a United States Patent 0 3,086,140 Patented Apr. 16, 1963 Further, thelight-output level of the lamp is controlled in a novel manner, as byvarying the voltage across the lamp-ballast series circuit, and arelatively high supply voltage is employed, up to volts A.C. It may beobtained from anauto transformer in the circuitary, with a tappedprimary or secondary winding.

Several of the presently preferred embodiments of these, and otherconcepts are diagrammatically and representationally illustrated, by wayof example only, in the accompanying drawings. The embodiments will bedescribed more in detail hereinafter with reference to these drawings.

In these drawings:

FIGURE 1 is a circuit diagram, embodying the present invention, for alighted locus that employs but a single lamp; and

FIGURE 2 diagrammatically illustrates a substantially complete system,according to this invention, for the crewcompartment or one bay, orother large segment, of the cabin of a jet transport aircraft.

In the arrangement shown in FIGURE 1, for a T-S, 13- watt fluorescentlamp 10, there is provided a source 12 of 115 volts, 400 c.p.s. of A.C.energy for the lamp. A conductor path 14 leads from 12 toward thegrounded primary winding 16 of a filament transformer 18, this conductorpath dividing as shown at a conductor path 20 which leads to abrightness control unit 22. Conductor 20 terminates in a slidingcontact, or the like, 24. Sliding contact 24 is adapted to make contactwith any one of a plurality of tap-points 26 on a ground voltageautotransforrner 22 to thereby vary the voltage fed from 22 toward thelamp filaments, thus to vary the brightness of the lamp as desired. Thefed-out voltage may vary from O to 425 volts, from the 115 volts A.C.source 12.

The other path, 30, extending onwardly from the junction of 14 and 20,terminates in the grounded primary winding 16 of a filament transformer,18.

interposed between the primary and two secondary windings 37 of 18 is adual-function, angled and saturable core 36. One leg 38 of core 36serves the secondaries 37 of the respective lamp filaments and the otherleg serves a ballast 50. The ballast 50 is a heavy-duty, inductiveimpedance ballast and is connectel to the autotransformer, 22, at itsinput end, the output end of the ballast unit being tied into one of theelectrodes or filaments 52 of the lamp, 10, via the conductor path,shown, from one of the secondaries 37. The combination of transformer18, core 36 and ballast 50 comprises a peak ing transformer having aprimary winding 16 and a secondary ballast 50 winding. The conductorpath provided by the other secondary 37 ties into the other filament 54of 'the lamp. Intermediate its ends this other secondary segment isgrounded and also connected to a ground-plane plate 56. Ground-plane 56physically parallels the lamp at a distance not over ,1 inch therefromand serves to enhance ionization in the gases, among other functions.

In FIGURE 3 a more or less complete lighting system for the crewscompartment of a jet engine transport aircraft is showndiagrammatically. Here, the same fundamental concepts and principlesthat are set forth hereinabove are employed; however, four T-5, 13-wattlamps 10 are arranged in electrical parallel, being energized by a 115volts, 400 c.p.s. source 12, as before. More specifically, energy is fedin parallel to the primaries of four filament transformers essentiallythe same as 38, from a source 12 by means of a conductor network 70.

A common ground is provided for the primary winding of each of the fourfilament transformers, the windings being connectedin parallel by meansof a conductor path network 60.

Each filament transformer has, as before, an angled,

dual-function, saturable core 36, interposed between the primary windingand the secondaries. Here, however, the conductor 60 is shunted acrossto the upper one 100 of the secondary coils in order to providecommunity of grounding of one end of one of the secondary coils. Thedistal and electrodes or filaments and the groundplane plates of allfour lamps are grounded by 60.

Each secondary winding is connected to a respective filament.Secondaries 100 are connected to the distal filament, whereas the lowersecondaries are connected to the proximal electrodes.

The upper leg A of core 36 serves the secondaries of the respective lampfilaments, and the lower leg of the angled core serves the ballast means50 as before, the ballast 50 being connected, as before to a brightnesscontrol unit, not shown, but indicated at 102 and constituted in thesame manner as the voltage autotransformer 22 set forth in describingFIGURE 1.

As before, the combination of filament transformer, core and ballastcomprises a peaking transformer, and a ground-plane plate 56, as, andfor the purposes previously described, is provided for each lamp.

By means of the concepts and arrangements set forth herein above, asystem designed for a nominal lamp current value of 100 milliamperes perlamp will give a dimming ratio of 100:1. With a system designed for anominal lamp current of 150 milliamperes, a dimming ratio of 1000z1 willbe obtained.

It is now perceivable that employing the foregoing concepts, dimming canalso be achieved by utilizing a very high frequencypower supply, greaterthan 400 c.p.s., giving rise to even greater lamp efficiency anddiminishing the number, size and weight of the adjunctive means. Also,substantially the same objectives could be attained, utilizing theaforedisclosed principles, except that control is accomplished bysaturating the series impedance ballast, thus decreasing the weight,size and volt-ampere capacity of the control-unit for the dimming means.

Although certain arithmetic parameters, geometrical shapes andcompositions have been hereinabove employed, for the sake ofconcreteness, it is to be understood that, notwithstanding, the scope ofthe invention is not limited thereby and is of the breadth defined bythe sub-joined claims.

Iclaim:

A fluorescent lamp lighting and dimming system, comprising:

a source of AC. energy providing alternating voltage of a relativelyhigh predetermined frequency;

an autotransformer including an input and an output,

said input being connected to said source and adjustable to.vary anoutput voltage from said output;

a substantially independent filament transformer including a primarywinding connected to said source, and first and second secondarywindings;

a substantially independent ballast providing a high series impedance atlow and medium lamp current operation, and including an inductivewinding having one end connected to one side of said autotransformeroutput;

a saturable core connecting said filament transformer and said ballastin a peaking transformer arrangement wherein said filament transformerprimary winding serves as a primary winding for said peaking transformerand said ballast winding serves as a secondary winding for said peakingtransformer; and

a fluorescent lamp including first and second filaments connectedrespectively to said first and second secondary windings of saidfilament transformer, and a ground-plane plate connected to ground, saidgroundplane plate and the other side of said a-utotransformer outputconnecting with said first filament, and the other end of said ballastwinding connecting with said second filament so that saidautotransformer output voltage is applied to a series combination ofsaid ballast winding and said fluorescent lamp,

said filament transformer providing continuous energization of saidfirst and second filaments, said autotransformer providing an adjustableoutput voltage to said ballast and series connected fluorescent lamp forvarying light output of said lamp, said high series impedance ballastproducing re-ignition of said lamp at a substantially constant phaseangle each half-cycle at low and medium lamp current operation tominimize striations, and said relatively high frequency of said source,said high series impedance of said ballast and said peaking transformerarrangement providing, when finite current flows through said lamp, asharp, steep wavefront lamp re-ignition peak at the beginning of eachhalf-cycle of that portion of voltage impressed across said fluorescentlamp which is due to said autotransformer output voltage applied to saidseries combination of said ballast winding and said fluorescent lamp,whereby stable operation of said lamp over a wide light output dimmingrange is obtained.

References Cited in the file of this patent UNITED STATES PATENTS2,665,394 Arvidsson Jan. 5, 1954 2,774,917 Passmore Dec. 18, 19562,829,314 Vranderburg Apr. 1, 1958 2,830,232 Carpenter et a1. Apr. 8,1958 2,864,035 Davis Dec. 9, 1958 2,961,579 Roney et a1. Nov. 22, 1960

